Jon Galloway

WordPress feeds offer a choice between Full Text or Summary. The Full Text option is preferable in a lot of cases (e.g. for a podcast), but the feed can grow very large.
One problem with a large feed is that if can exceed the <a href="http://support.google.com/feedburner/bin/answer.py?hl=en&answer=79009" rel="nofollow ugc">Feedburner 512K limit</a>. Your feed may be valid when you first set it up, but eventually when your feed gets big enough, Feedburner will stop updating.
This plugin gives you another setting (available on your Settings / Reading admin page) which sets how many posts should have Full Text. All posts after that will be shown as Summary. This gives you the best of both options – Full Text for new posts, and Summary for older posts. 
<h3>Readme Generator</h3>
This Readme file was generated using <a href='http://sudarmuthu.com/wordpress/wp-readme' rel="nofollow ugc">wp-readme</a>, which generates readme files for WordPress Plugins.

Excerpt Old Posts

This plugin solved my problem with feedbruner.



Greate idea

Shows excerpted content for older posts. This allows more items in the feed while working around the Feedburner 512K feed limit.

Tobias Eisenschmidt

RSS Links Manager lets you easily customise your RSS links via WordPress’ admin menu. Are you using Feedburner? Just enter your Feedburner URL. Are you using Disqus or Facebook comments instead of WordPress’ internal comment system? Just deactivate the feeds you don’t need – including category, tag and author feeds.
Features:
<ul>
<li>Customise your feed links (title, URL, MIME type)</li>
<li>Remove individual feed links (main feed, comments, extras)</li>
<li>Directly hooks into WordPress’ wp_head functon</li>
<li>Multilingual (English and German)</li>
</ul>

RSS Links Manager

Manage and customise your RSS feed links.

Excerpt Old Posts vs RSS Links Manager